600 crew members and 500 extras spent more than three weeks filming in a secluded valley of Northern Ireland, working tirelessly to bring this epic brawl to life. Sloan was on hand to document the actors as they played out one of the greatest fight scenes in "Game of Thrones" history.

"You can't explain what it's like to work on sets like that because there's just so many things going on at once," Sloan told Tech Insider.

"Iwan [Rheon] is such a nice guy and as soon as the camera rolls he just turns evil. I just love it, I loved watching that whole sequence play out, it was great," Sloan told TI. Helen Sloan/HBO Sloan was smack in the middle of many of the fight sequences during shooting for "Battle of Bastards." That meant getting her hands a bit dirty as she stood amidst the action.

"No one's ever going to get hurt because the safety element is so high ... but [the stuntmen] have done a hundred sword fights and I've done none, so my fear is still very real," Sloan told Tech Insider. "You're right in the middle of it, you can hear the woosh of the swords ... it's that good fear, like a rollercoaster. Because it's maybe a minute and a half of 'Whoaaaa' and then 'Woo, okay nice.' and then you look through the photos and you think 'Whoa that was awesome.'"

Here's one of the many epic action shots Sloan captured on set:

These are the types of action shots Sloan needs to be up close to capture. Helen Sloan/HBO "You can't shoot that from far away, you can't just go on a long lens and shoot it," Sloan said. "It just doesn't feel right ... If you're not willing to get in and get dirty and get in the muck then you're not going to get the action shots."

The "dirty" aspect of shooting "Battle of the Bastards" didn't just come from mud on the ground.

"[There are] these special little handheld cannons that the props and special effects guys have, and they were full of mud and blood," Sloan explained. "So as everyone's dancing around trying to stay behind the cameras, these guys are firing off these mini explosions. You come out of the shot — they shout 'Cut!' — and you just look at everyone and everyone's literally splattered. We look like we've been massacred."

"I think the scariest moment for me was when we were filming the horse stampede," Sloan said. "You're just standing there with 60 horses running at you. I mean, to be fair, the hardest job in the room that day was Kit's [Jon Snow], because he was much closer to them than we were."

Though this photo was not captured by Sloan, she was standing just behind the camera during filming. HBO "We were safe but still I've never had a wall of 60 horses running at me so my heart was beating a little fast," Sloan said, laughing. "The tension was there, the fear was there ... I think I had a series of tiny heart attacks that day."

Aside from the literal cavalry of horses assembled, one of the greatest feats involved with "Battle of the Bastards" was the gigantic pile of bodies stacked on the battlefield. "There were real guys in there, real stuntmen amongst the mannequins," Sloan said. "So they're lying in that pile while a hundred other guys run up it, skillfully avoiding standing on the real guys' faces."

The body pile can be seen in the background of this shot from Sloan. Helen Sloan/HBO "You're standing there in this constant state of 'Oh my god, oh my god, oh my god,'" Sloan said. "But we got through. It's nice for me because I'm just the documentarian, sort of wandering around looking at all this amazing stuff, and just marveling at the crew and the cast."

The enormous group of extras and stuntmen on set was unparalleled in "Game of Thrones" history. Not to mention the live horses and visual effects team on hand.

"The tenacity of the crew and the extras — it was just relentless. Like, really relentless," Sloan said. "Those extras just ran up and down and up and down the field, screaming, for weeks. They did such a great job."

Sloan's portraiture of the cast this season has been stellar. Helen Sloan/HBO Sloan has been part of the "Game of Thrones" crew since the very beginning of season one. Despite having a totally irregular relationship with the show's storyline and characters (what with constantly being behind the scenes) she still gets caught up in certain tender scenes.

"There are moments on set when you just can't help getting a little bit emotional," Sloan said. "For the people watching it's ten hours — but for us [the crew] it's almost ten years of work. It's so hard to explain ... I don't know what it's like to be on the outside but there are moments where I do say, 'Awwww that's good, thanks David and Dan for that, that's a nice moment.'"

For example, one of Sloan's favorite moments of the season so far was the reunion between Jon and Sansa in episode four, "Blood of My Blood."

Jon Snow (Kit Harington) and Sansa Stark (Sophie Turner) embracing was an emotional scene to shoot. Helen Sloan/HBO Filming sequences like "Battle of the Bastards" may be demanding work, but Sloan recognizes the privilege of being on set every day.

"Every year I do something on this job that I've never done before and probably will never do again," she said. "By the very nature of the show, the experiences I'm having as a photographer are just incredible. I don't think I'll ever be on a show again where I'll have a wall of 60 horses and a sword fight right in front of my face."